1. Field of the Invention
The present invention relates to an information device and a controlling method of the same, and particularly relates to an information device including a heat-producing internal unit which produces heat by operating continuously and a controlling method of the same.
2. Related Background Art
In recent years, multimedia information devices represented by a digital video camera and a digital still camera have become rapidly widespread. Accordingly, between a computer and an information device (especially a portable device) having a storage function (information storing/recording function), not only normal data files but also so-called multimedia file data including video data, image data, music data is frequently exchanged.
The capacity of a multimedia file (especially image data) is generally a large capacity although it varies according to factors such as a file format, compression ratio, and recording time. High-speed serial interfaces such as an IEEE 1394 bus and a universal serial bus (hereinafter referred to USB) have been increasingly used for transferring this multimedia file.
If data is exchanged between these computer and peripheral information device via the USB interface or the like, the temperature of a recording unit (hard disk, for example) of the information device increases due to long-time continuous access from the computer. Hence, the need for taking some measures in order that the temperature of the recording unit does not exceed a temperature prescribed by the information device itself arises.
Such temperature increase causes a notable problem especially in potable information devices including a notebook PC, a PDA (Personal Digital Assistant), and so on for the following reason.
Namely, exceeding the usable temperature range of the hard disk or the like may cause a malfunction, but since production merits of the portable information device are size reduction and weight reduction, it is difficult to take measures against heat release physically accompanied by weight increase and size increase of the product.
As for the portable information device, a user may manipulate it while holding its product body directly in his or her hand or while holding it on his or her lap, or carry it while holding it in a clothes pocket. At this time, if the temperature of the recording unit such as the hard disk inside the device becomes higher in his or her hand, on his or her lap, or in the pocket, the product body which the user can touch heats up, and this heat may cause the user discomfort.
To prevent the surface temperature of the product from increasing and exceeding a certain temperature, it is necessary to measure the ambient temperature of the hard disk or the like, and if the temperature approaches a set vale, to take appropriate measures to decrease the temperature.
In the recording unit such as the hard disk, similarly to other electronic components, modules, and units, the rated temperature is determined by its own usable temperature (which includes operation guaranteed temperature, performance guaranteed temperature, surrounding environment temperature) range specification, and therefore it is necessary to set a threshold of the detected temperature by considering performance variations of respective products in addition to the value of the rated temperature and adding a margin.
Incidentally, Japanese Patent Application Laid-open No. 2000-20253 (hereinafter referred to Patent Document 1) discloses an image recording device which performs temperature control to prevent image degradation accompanying temperature increase of a recording head. This image recording device is connected to the computer not by a USB but by an IEEE1394 bus, and the object whose temperature is to be decreased is limited to the recording head of the image recording device.
The following measures are generally taken in order to decrease the temperature as described above.
(1) A physical measure in which a large radiator or cooling fan is mounted or a vent hole is provided in a component or a unit which produces heat.
(2) A measures in which the temperature increase of an information device is reported to a computer as a data transmitter by communication exchange between the computer and the information device via the USB to suppress access.
However, the measure in (1) causes a physical increase in the size of a casing and an increase in noise due to the fan. Also this causes cost increase because of additional components or an increase in the number of man hours for mounting.
Moreover, as concerns the measure in (2), the USB interface is a standard specification having a master-slave relationship in which a computer as a host is a master and an information device as a device is a slave. The host as the master manages communication with the information device, and the communication is first started by the host and progresses by the device giving a reply to the host.
Therefore, in order that the host knows the temperature of the device and performs some control, for example, processing of making a request to confirm and transmit temperature data inside the device from the host to the device, analyzing the data transmitted from the device, and performing processing to reduce the amount of transmit data when it is necessary to decrease the temperature becomes necessary. However, to realize this, the host also needs driver software of its own.
The production of the software and incorporation thereof into the host device cause many harmful effects such as problems of a period and a cost required for development, a cost required for driver distribution, an installation work of a manufacturer or a user, and the operation guarantee of each computer.
Unless the processing of incorporating the software of its own into the host is performed, the surface temperature of the target unit in the information device approaches an upper limit of the usable temperature, and even if there is a possibility that the surface temperature exceeds the upper limit, this cannot be reported from the information device as the slave to the computer as the master. Accordingly, in a communication interface with such a master-slave relationship, it is desired that access to the heat-producing internal unit such as the hard disk be able to be stopped by a simple method. Moreover, also in a communication device without a mater-slave relationship, it is convenient that the access to the heat-producing internal unit such as the hard disk can be stopped by the simple method.